Field of the Invention
The present invention relates particularly to an image processing device, an image processing method, and a program favorably used to generate an image with an enlarged dynamic range.
Description of the Related Art
A high dynamic range (HDR) technique has been known in the past in which positions in multiple images having different exposures from one another are aligned and then the images are composited, thereby realizing an image with an enlarged dynamic range. In the HDR technique, however, in order to composite the images having different exposures from one another, it is required to carry out the composition such that tone jump that can be generated by frames with different brightness is not noticeable. Taking this into account, the conventional technique has composited images in such a manner that tones of the images having different exposures from one another are compressed using tone curves while the brightness is adjusted. As a result, an image with the enlarged dynamic range has been generated in which the tone jump is not noticeable with ease. However, the tone compression and the brightness adjustment using the tone curves have caused a problem of reduced contrast.
For a solution to this problem, for example, methods described in Japanese Patent Application Laid-Open No. 2012-29029 and Japanese Patent Application Laid-Open No. 2010-98616 disclose a technique for generating an HDR image with high contrast in which the images having different exposures from one another are composited and then a gain characteristic is determined based on an image of a luminance distribution after the composition to carry out tone processing.
In the conventional technique disclosed in Japanese Patent Application Laid-Open No. 2012-29029 and Japanese Patent Application Laid-Open No. 2010-98616 described above, however, the tone processing is applied again to the image after the composition through the gain processing, resulting in a problem of an increased noise amount. It is considered in this situation that noise reduction processing is applied after the composition to suppress the increase in the noise amount. However, the images are deformed during the position alignment among the multiple images, bringing a problem of degradation in band occurring within a frame in accordance with a deformation amount. This accordingly causes difficulties in applying the optimal noise reduction processing and optimal edge enhancement processing to the image composited after the position alignment.
Taking the above-described problem in consideration, an object of the invention is to make it possible to generate an HDR image with high contrast and a favorable image quality.